Separation of the constituents of gaseous mixtures



Oct. 20, 1925- c. c VAN NUYS SEPARATION OF THE CONSTITUENTS OF GASEOUS MIXTURES Filed May 24, 1923 C lNvENVT oR M M: v BY z a; M; &&.m

1M ATTORNEYS Patented Oct. 20, 1925.

UNITED STATES 1,557,907 PATENT. OFF-ICE;

. cLAunE c. vAN NUYS, or CRANFORD, NEW JERSEY, Assronoa'ro AIR nEnuc'rIoN COMPANY, nvconroa ran, or NEW YORK, N. Y., A CORPORATION or mzzw YORK.

sErAaATIon or THE consrrrurmms'or GASEOUS MIXTURES.

To all whom it may co rwem:

Be it known that I, CLAUDE C. VAN Nears, a citizen of the United States, residing at Cranford, in the county of'Union, State of New Jersey, have invented certain new and useful Improvements in Separation of the Constituents of Gaseous Mixtures; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. I

This invention relates to the liquefaction of ternary gaseous mixtures for the purpose of recovering the constituents thereof in a theoretically and commercially economical manner. The method employed is particularly adapted for the separation of the PIlIlcipal constituents of air, which, for the purpose of this disclosure, is considered to becomposed of oxygen, nitrogen and argon, thereby disregarding the minute quantit es of rare gases present. It may be applied for a like purpose to other ternary mixtures, the constituents of which have difi'erent boiling points. I

It has been proposed heretofore to separate the constituents of a ternary gaseous mixture such as air by liquefaction and subsequent rectification. The methods used have, however, relatively low eificiency when compared with the theoretical possibilities.

It is the object of this invention to eliminate many of the sources of energy loss and to otherwise improve the methods of separating the constituents of ternary gaseous mixtures as heretofore practiced by avoiding as far as possible all thermodynamically irreversible operations in connection wit the production and utilization of the refrigerative effect required in the liquefaction cycle.

A further object of the invention is the provision of a method of and apparatus for the production of argon from the atmosphere in an economical and efiicient manner, accompanied by the recovery of oxygen of higher urity than has heretofore been possible in liquefaction operations, owing to the difliculty experienced in sepa rating argon therefrom.

Further objects and advantages of the in- I vention will be apparent as it is better understood with reference to the following Application filed May 24, 1923. Serial No. 641,035.

specification and accompanying drawing d1a ammatically illustrating the a aratus which 1s adapted for use in practicmg the invention.

Itis to be understood that in the drawing no attempt has been made to illustrate those portlons of liquefaction apparatus which are well known to those skilled in the art, the purpose of the drawing being merel to assist the reader to a complete compr enon of the essential features of the inven- In common with the method disclosedin my copendlng application, Serial No. 615,- 036, filed January 26, 1923, the separation of the three constituents is accom lished in three successive steps, each oft ese steps embodying fractional condensation .and separation. The first step consists in separating the compressed and cooled air into two parts by selectively liquefying a portion thereof, employing for that purpose in the greatest (possible degree the method of backwar return. This step results in the separation of a fraction, consisting approximately of half by volume of the air treated, composed of substantiallypure nitrogen, the

other fraction being a ternary mixture of oxygen, argon, and nitrogen in the liquid state, with the percentages of the two form-' or constituents substantially greater than in air, for example, oxy n argon 2% and nitrogen 53%. T e nitrogen fraction which is available at a pressure of from four to six atmospheres is liquefied, and a portion of the liquid is utilized in the second step. The balance of the liquid nitrogen is utilized in the third step as hereinafter described.

Thesecond' step of the operation consists in separating by a, suitable rectification the portion enriched in oxygen and argon into two sub-portions, one of which .is a gaseous efiiuent having a composition of substantially pure nitrogen, while the other contains from 93 to 95% oxygen nd practically all of the argon content of the original air. The low temperature of the nitrogen etfluent is utilized by means of suitable interchangers to cool the system and is therebyrestoredto substantially the ,ori 'nal air temperature. This sub-portion is available at atmospheric pressure, and after 'ving up its cold to the system it is rejecte or uti ized for any desired purpose. The. sub-por ion of 93 to. 95% oxygen is available in the liquid state, and in a manner similar to that described in said co-pending application is delivered to an intermediate point of the auxiliary rectification column. In this auxiliary column the third and last step of the separation is accomplished, this stepconsist- 'ing in the production of oxygen of high purity in the liquid state and an argon product containing. a small amount of oxygen and only a very minute quantity, if any, of nitrogen. A small amount of substantially pure nitrogenis also separated in this step as a residual uncondensed gas, which is re- I for efi'iciently applying a suflicient amount primary cycle.

of refrigerative efl'ect directly to the auxiliary liquefaction cycle to overcome the effects of heat leakage therein, so that the liquid 0 gen returning to the primary from the auxi iary column. is somewhat greater than the amount necessary to constitute the total oxygen product of the separation. The present method differs from that described in said co-pending ap lication in that part of the refrigerative e ect applied to the auxiliary cycle is produced in a somewhat difierent manner whereby the amount of the working fluid necessary to be compressed and cycled through the auxiliary apparatus is very much reduced, and thus an important economy in the cost of operation of the apparatus is accomplished.

In the co-pending application, I have pointed out that the amount of residual uncondensed nitrogen obtainable at the top of the tubular system constituting the primary backward return vaporizer, wherein .the initial selective condensation is accomplished, is considerably in excess of that necessary, after liquefaction thereof, for subsequent use as reflux liquid nitrogen in the This excess residual nitrogen is utilized, after being brought into indirect contact with succeeding portions of the incoming air, as a working fluid in an expansion engine or turbine, whereby it attains' an extremely low temperature, and becomes a suitable refrigerant for use at a suitable point in the system.

In the operation of that method,- however, it is diflicult, particularl in an apparatus of the size-in commercial use to-day, to attain a 'high efiiciencyin the expansion of equivalent of the liquid the residual nitrogen passing through said expansion engine or turbine on account of the relatively small amount thereof available for that purpose. Moreover, when the expansion machine is of the reci rocating t it is diflicult, on account of t e ulsations induced by the machine in the tu es of the primar vaporizer, to maintain a sufficiently higi purity of the residual uncon densed nitrogen so that, after liquefaction of the portion necessary for that pur ose, it is suitable for use as reflux in tiie primaryl column. I

I ave discovered that that portion of the residual nitrogen not necessary for reflux needs may be utilized in a much more efiicient manner to reduce the cost of operating the system, with the further advantage that no expansion machine is required. In the operation of the method. forming the subject of this disclosure all the residual uncondensed nitrogen available at the top of the primary vaporizer is liquefied in the reux condenser of the primary column; but only as muchof the liquid thus produced as is necessaryias reflux in the primary column is utilized for that purpose. e remaining portion of the liquid nitrogen is delivered to the s ace surrounding the tubes of a condenser oca-ted at the top of the auxiliary rectifier. All or a portion of the vapors ascending in the auxiliar rectifier pass through the tubes of this con enser and is subjected to selective liquefaction therein. Experiments as well as calculations show that about twice as much residual nitrogen is available at the to of the primary vaporizer as is necessary or reflux needs in the primary cycle and that the portion of this residual nitrogen which is not needed as primary reflux nitrogen in the auxiliary condenser, reduce the amount of liquid necessary to be cycled in the auxiliary cycle by approximately one half in producing a given composition of argon product and high purity oxygen liquid.

Another advantage of thus utilizing the liquid nitrogen is that it assists in overcoming the effects of heat leakage in the auxiliary cycle. In my co-pending application. I have pointed out the eflects'of heat leakage in the auxiliary cycle and the advantage of overcoming said effects by the use of an auxiliary liquefier. This advantage consists in the fact that by the application of refrigerative effect directly to the auxiliary liquefaction cycle, the liquid oxygen returned to the primary from the auxiliary column is somewhat gi'eater'than the amount necessary to constitute the total oxygen product of the separation. Since any refrigerative efl'ect, however, applied to the auxiliary cycle, will product the same result, it is apparent that the present invenwill, if it is applied as liquid "primary liquefier, and for this'reason any tion secures the advantage just pointed out catio'n. I 7

Another advantage of the use of the auxiliary liquefier as described in said co-pending application is' that the liquefaction accomplished in that liquefier is produced by the cold outgoing productsof the primary apparatus before they pass .through the liquefaction accomplished in the auxiliary 'liquefier reduces by an equivalent amount the liquefaction necessary to be accomplished in the primary liquefier. In the operation of the method forming the subject of the present disclosure, theliquid nitrogen delivered to the, auxiliary cycle is produced in the primary cycle, and hence the refrigerative efiect thereof in-the auxiliary cycle will not reduce the amount of liquefaction necessary to'be accomplished in the primary liquefier. Therefore, in common with the method disclosed in said co-pending ap lication, provision'is'made, in the method ibrming the subject of the present disclosure, for an auxiliary liquefier. The-amout of liquefaction necessary in this'liquefier is, however, somewhat reduced, being only that necessary to compensate for heat leakage in the auxiliary cycle. This" heat leakage has been much reduced on account of the fact that the amount of working fluid cycled in the auxiliary apparatus is, by the operation of the present method, much reduced. The effect is therefore cumulative.'

For convenience the i-nventionwill be described in more detail with reference to the drawing, the primary and auxiliary columns being considered separately. The primary column comprises a shell divided by partitions 6, 7 and 8 into a lower rectifying compartment 9, vaporizing compartments 10 and 11, and upper rectifying compartments 12 and 13'. The gas to be treated, after compression and cooling, 'is preferably divided into two portions, and one portion is delivered through a pipe 14 controlled by a valve 15 to an expansion engine 16 wherein it is expanded with external work and thereby cooled. The cold expanded gas passes through a pipe.17 to the compartment 9 of the column. The balance of the cold compressed gas is delivered by a pipe 18 to a. liquefier 19 wherein it is cooled by cold gaseous products of the column passing through tubes 20 and 21 as hereinafter described. The cold compressed gas is thus liquefied, andthe liquid is deliveredthrough a pipe 22 controlled by a valve 23 to the compartment 9 of the column near the upper end thereof. This liquid flows downwardly over trays 24:. of the usual kind employed in rectifying columns and is thereby subjected to the rectifying action of the expanded gas which enters through the pipe 17. An initial rectification of this liquid together with other li uid formed by selective liquefaction of t e rising as occurs and a of the compartment which approximates a. composition which is in phase equilibrium with the gas entering through the pipe 17.

The liquid accumulatin 'in the bottom of the compartment 9 is delivered b a pipe 25through a pressure-reducing va ve 26 to quid product gathers in t e bottom? the rectifying com artment 13 of the column and accumulates a out a condensercompris- I flows through a tube 28 and passes thence downwardly over trays 29 of the usual ty e employed in rectification columns and is su t jected to vapors rising throu h the column. The rectification of the liquid is thus accomplished, and as it escapes it becomes more and more impoverished in the least condensible "constituent. The liquid accumulates in a container 30 within the column and overflows into the compartment 11.

The entering gas with the vapors rising from the compartment 9 passes through a lurality of tubes 31 which are surrounded y liquid accumulated as described in the container 30 and com artment 11 and by liquid which is supplie to the compartment 1-0 as hereinafter described. The refrigerative effect of this liquid causes selective liquefaction of the entering gases and results in the separation of the liquid which flows backwardl into the compartment 9 from an unliquefie residue which continues through the tubes 31 to a header 32 with which the tubes communicate. This unliquefied resi: due escapes through a pipe 33 and is delivered to a header 34 communicating with the tubes 27 of the condenser. These tubes are surrounded by liquid, and during the passage of the gas through the tubesit is liquefied and descends into a header 35. A pipe 36 communicating with this header and provided with a'valve 37 permits the diversion of a portion of the liquid to the upper part of the rectification compartment 13. This liquid is the reflux which flows downwardly over trays 38 ofthe type usually employed in rectification columns and. by contact with the rising vapors is impoverished in the least condensible constituent. The vapors from the compartment 12 enter thecompartment 13 through a-pipe 39 and thence pass upwardly through the trays 38.

As the result of the operation as described, a liquid and an unliquefied residue are first produced. In the treatment of air the liquid contains substantially all of the oxygen and ar on and some of the nitrogen of the air. e unliquefied residue. is substantially pure nitrogen. and a portion of the liquid is employed as a This nitrogen is liquefied ing a number of tubes 27. The liquid overreflux inthe second or rectification step of theprocess which results in the separat on of liquid produced'by selective liquefaction into a gaseous eflluent which is also sulistans more, and substantially all of the argon originally1 tiallypure nitrogen and a liquid containing a large proportion of oxygen,,e. g., 93%,or

present in the air. The eflluent escapes t rough a pipe 40 and after utiliza-I tion as a refrigerant as hereinafter de-'" scribed it may jected.

Toaccomplish the separation of the rich oxygen liquld containing argon into its con-.- stituents, an auxiliary column 41 is em beemployedas desired or re-f ployed. This column comprises a'shell di mary column which is not vaporized therein is delivered by'a pipe 51 controlled-bye valve 52 to an intermediate point Of thB'IBYQ- tifying compartment 49 and flows downwardly therein over trays 53 of the kind usually employed in rectification column's wherein it 1s subjected to the rectifymg action of the va ors rising throu h the column. The ownwardly flow ng liquid passes throu h a pipe 54 into the compartment 48 an overflows through a pipe 55; into the compartment 47. During its passage the liquid is freed from the more read ily vaporizable constituents, for example, nitrogen and argon, and. the liquid accumulating in the compartment 47 is substantially pure oxygen. This liquid is returned through a pipe 56 to the compartment 10 of the primary column where it is vaporized by the passage of gas through the tubes 31.-

The vapors rising throug the rectifying com artment 49 are subjected in the upper portion thereof to liquid supplied as hereinafter described and flowing downwardly over trays 57 of the usual kind employed in rectification columns.v The vapors which contain a high (percentage of argon with some oxygen an nitrogen pass upwardly through tubes 58 which extendthrough the a condenser compartment 50. This compartment is filled with liquid nitrogen delivered 7 through a pipe 59 controlled by avalve 60 from the header 35 of the primary column.v The liquid thus supplied is the portion of the liquid which is not employed as reflux in the-primary column. The liquid in the condenser 50 is vap'orized and the vapors passing through the tubes 58 K are concurrently subjected to selective liquefaction resulting in the separation of the more readily condensible constituent, oxygen, for example, which returns through the tubes into the compartment 49. The remaining va- .pipe 63 without passin .pors escape through a pipe ,61 to an ex "chang'er 62. A portlon of the va ors from the column 41 may bev diverted t rough a through the tubes 58 of the condenser an likewise delivered nicates with a compartment-Mat the end of the exchanger andlthekzpi pe'63 likewise communicates 'with ia ':1compartment :,65.; 7 to correspondin com artments '68- and69 at a the opposite en oft e: exchangerqsrkpipe Y a 70 controlled by avalve71delivers'the' gas entering the compartment .68 ,to a gasometer 172 in'which it is stored, this vgas of the products of the-operation, for exam-' ple, argon. The gas entering the compart Tubes66 and-67 connect these compartments sing on ment 69 asses through a pipe 73 toa com- 4 where it is recompressed and cooled by the usual intercoolers. From the compressor the gas passes througha pipe 75 to t e exchanger 62 wherein ticirculates aboutthe tubes 66 and. 67, being cooled by jthe' gases passing'through -these tubes. .By

means of a by-pass 61' and valves 62 and .63? theoperator mayrc'ause all oft-the va ,porsfrom the column 4lvto pass 'throu h the tubes 58 and thence to the compressor 4, or

all of the" vapors may-be directed through the tubes 58 tothe gasometer 72.-- -Thus' 'when the valves 63 and 73 are closed '2 1I1d the valve 62' is-open all ofthe va ors will be recom ressed.. If thevalves-62 and 63' are close the ,vapors will pass to the asometer. or-

63' and 71 are open to permit operation as hereinbefore described. 3

- From the exchanger 62 the cooled as is vdelivered by a pipe 6 to' an auxilia iquefier 77 and passes therein about a p ura 'ty.

of tubes 78 through which a cooling agent such as the eflluent from the primary column is caused to travel. For-[this purpose a pipe .79 connects-the ipe 40 with a' compartment 80 at the en of the liquefier 77. After passing through the pipe 78 the gas is deivered through a compartment 81' and ipe 82. The gas joins the vapor 'formed .1n the condenser 50 which escapes through a ipe 83, and the combined gases are dethe liquefier 19. c

The gas which is cooled by its passage through the auxiliary liquefier 77 and partially or wholly liquefied is delivered through a pipe 85 to the lower compartment 46 of the auxiliary column. It passes thence upwardly through tubes 87 which are surrounded by the bodies of liquid in the compartments 47 and 48; Selective liquefaction of the gasinthe tubes results, and the liquid flows and is thence delivered through a pipe 88 and pressure-reducing valve 89 to the upper and the valve 71 is open, all of- -mally the valve 62-is close and the valves.

ivered to a' compartment 84at the end of x ackwardly into thecompartment 46 part ofthe rectification compartment 49 as ereinbefore described. This liquid is substantially free from the most volatile con- 2 through a pipe. 93, and a portion thereof may be returned through a pipe 94 to the compartment 47 of the auxlllary column. These vapors, together with the vapors formed in the compartment, pass upwardly.

gases escape through pipes 112 and 113 which may communicate with stora e receptacles or may'deliv'er the gas to 't e atmosphere, depending upon whether it is to be used or re ec d.

The gas entering the system is introduced through a pipe 114 to the exchanger 102'and passes about baflles 115 in contact with the tubes 108 and 109. The gas is thus cooled and is delivered through a pipe 116 with which pipes, 14 and 18 communicate- It is understood that'prior to its introduction to the exchanger 102 the gas'entering the system has been compressed and cooled in the usual manner.

The purpose of the invention has been through a pi e 95 and mingle with the discussed heretofore but attention is particuvapors forme in the compartment 48. The larly directed to the utilization of the liquid vapors rise throu h thedescending liquid to produced in the tubes 27 for coolin the accomplish recti cation thereof. The retubes 58 Of the condenser and t0 the a. van;. sult of the operation as described is the ges f his mode of Operation as hereinradual enrichment of the gas circulating/before enumerated. It is to be observed that 1n the auxiliary cycle until it includes a de a ls as to the amount of gas passing high proportion of ar on and is suitable for through th1s condenser or circulated indewithdrawal as a pro uct of the operation. This withdrawal is preferablyaccomplished after the gas has assed through the condenser 50 and is t us freed from some or all of the oxygen which may still be included therein. It is possible in this manner to obtain argon substantially free from nitrogen and containing a very low proportion of oxygen and at the same time to materially reduce the amount of work necessary in the auxiliary cycle by limiting the amount of gas which is recompressed therein. The other product of the auxiliary column is substantially pure oxygen which is returned to the primary column in liquid form as hereinbefore described to be vaporized there- This oxygen vapor is withdrawn through a pipe 96 controlled by a valve 97 and is delivered to a compartment 98 at one end of the liquefier 19. It v passes through the tubes 21 of the liquefier to a compartment 99 at the opposite end and thence through a pipe 100 to a compartment 101 ,of an exchanger 102. The gas delivered to the compartment 84 of the liquefier passes through tubes 20 therein to a compartment 103 at the opposite end of the liquefier and thence through a pipe 104 to a compartment 105. A by-pass 106 controlled by a valve 107 permits delivery of the effluent from the primary column to the compartment 84 of the liquefier. This is particularly useful in starting the apparatus or in operating it independently of the auxiliary column.

The exchanger 102 comprises a shell with a plurality of tubes 108 and 109 through which gas. passes from the compartments 101 and 105 to corresponding compartments 110 and 111 at the opposite end of the exchanger. From these compartments the pendently thereof may be'varied and that this utihzation of the liquid from the primary column for refrigeration pur oses may be carried out in connection wit various modifications of the system which are described herein for illustrative purposes and without departing from the invention as herein set forth and claimed.

I claim 1. A method of separatin the constitu- I ents of gaseous mixtures, w ich comprises subjecting the compressed and cooled mixture to selective liquefaction to separate a liquid enriched in the less volatile constituents and a residual gas, liquefying the residual gas, rectifying the liquid enriched in the less volatile constituents with a portion of the liquefied residual gas, subjecting the liquid product of the rectification to an auxiliar rectification, and cooling the gaseous pro not of the auxiliary rectification by heat exchange with thebalance of the liquefied residual gas to separate the least volatile constituent therefrom.

2'. A method of separating the constituents of gaseous mixtures, which comp-rises subjecting the compressed and cooled mix ture to selective li uefaction to separate a liquid enriched in t e less volatile constituents'and a residual gas, liquefying the resiu al gas by heat exchange with the liquid enriched 1n the less volatile constituents, rectifying the liquid enriched in the less Volatile constituents with a portion of the liquefied residual gas, subjecting the liquid product of the rectification to an auxiliaryrectification and cooling the gaseous product of the auxiliary rectification by heat exchange with the balance of the liquefied residual gas to separate the least volatile constituent therefrom.

' 3. A method of separatin the: con'stituents of gaseous mixtures, w ich comprises subjecting the" compressed and cooled mixthe less volatile constituents with a Ioliquid product of the rectification to an aux-' ture to selective li uefaction to separate a liquid enriched in 31c less volatile constituents and a residual gas, liquefying the-residual gas, rectifying the liquid enriched in of the liquefied residual gas, 'subjectmg the iliary rectification, and cooling a portionpf the gaseous product of the auxiliary rectifi; cation by heat exchange with the balance of the liquefied residual gas to separate the least volatile constituent therefrom.

4. A method of separating the constituents of gaseous mixtures, which comprises subjecting the compressed and cooled mixture to selective li uefaction to separate a liquid enriched in t e less volatile constituents and a residual gas, liquefying the resid-.

ual gas, rectifying the liquid enriched in the less volatile constituents with a portion of the liquefied residual gas,-subject1ng the liquid product of the rectification to an auxiliary rectification, cooling a portion of the gaseous product of the auxiliary rectification by heat exchange with the balance'of the liquefied residual gas to separate the leastvolatile constituent therefrom, reli uefying the remainder of the gaseous pro uct of the auxiliary rectification and returning it for further rectification.

5. A method of separating the constituents of gaseous mixtures, which comprises subjecting the compressed and cooled mixture to selective liquefaction to separate a liquid enriched in the less volatile constituents and a residual gas, liquefying the residual gas, rectifying the liquid enriched in the less volatile constituents with a portion of the liquefied residual gas, subjecting the liquitl productof the rectification'to an auxiliary rectification,'cooling a portion ofthe gaseous product of the auxiliary rectification by heat exchange with the balance of the liquefied residual gas to separate the least volatile constituent therefrom, recompressing and reliquefying the remainder of .the gaseous product of the'auxiliary rectification and returning it for further rectification.

6. A method of separating the constituents of gaseous mixtures, which comprises p ual gas, rectfying the liquid enriched in subjecting the compressed and cooled mixture to selective liquefaction to separate a liquid enriched in the less volatile constituents and a residual gas, liquefying the residortion 7. A method of separatin the.constituents ofv gaseous mixtures w ich comprisessubjecting the compresse and cooled mixerant in the further separatlon of the'con stituents of the liquid produced by the first rectification.

8. A method of'separatin the constituents of gaseous mixtures, w ich comprises subjecting the compressed and cooled mixture to selective 1i uefaction to separate a liquid enriched in t e less volatile constitu- .der of the liquefied residual gas as a refrigents and a residual gas, liquefying the residual gas, rectifying the liquid enriched in the less volatile constituent with a portion of the liquefied residual gas, and utilizing the remainder of the liquefied residual gas as a refri erant in the further separation of the constituents of the liquid produced by the first rectification after the latter has been subjectedto a second rectification.

a. A method of separatin the constituents of gaseous mixtures, w ich comprises subjecting the liquid and vapors containing said constitutents to rectification, compressing a portion of the gaseous efliuent of the rectification, cooling it to separate one of the constituents from the liquid which is thereby impoverished in that constituent,

utilizingthe impoverished liquid as a 'recsaid constituents to rectification, compressing a portion of the gaseous eflluent of the rectification, cooling 1t to separate one of v the constituents fromthe liquid which is thereby impoverished in that constituent, utilizing the impoverished liquid as a rectifying agent in said rectification, subjecting the remainder of the effluent to cooling by heat exchange with an evaporating liquid to liquefy .and separate. the least volatile constituent and withdrawing the portion of the effluent thus purified.

11. A method of separating the eonstitu ents of gaseous mixtures, which comprises subjecting the liquid and vapors containing said constituents to rectification, conipress ing a portion of the aseous efiluent of the rectification, cooling 1t to separate one of the constituents from the liquid which is thereby impoverished in that constituent,-

utilizing the impoverished liquidlas a rectifying agent insaid m'ctification, subjecting the remainder Ofthe efiluent to coohng by heat'exchange with an eyaporatmg liqui to liquefy' and separate the least volatile constituent, withdrawing the port-ion of the eilluent thus purified and sup lying the liquid employed in cooling the e uent from a separate liquefaction cycle inwhich the liquid and vapors which are subjected to rectification are likewise produced.

12. A method of separating the constituents of ternary gaseous mixtures, which com rises subjecting 'a liquid and its vapors pro need from sald mlxture and contammg chiefly the least volatile constituent to rectification by means of a liquid containing another and more volatile. constituent, with-' drawing the gaseous efiluent of this rectification, separating a portion of the most volatile constituent from said gaseous efliuent by liquefying the remaining gas, utihzing this hquid in the rectification and when the eifluent has been sufliciently enriched in the constituent of intermediate volatility subjecting a. portion thereof to cooling to separate the least volatile constituent therefrom. a a

13. A method of separating the constituents of ternary gaseous mixtures, which comprises subjecting a liquid and its vapors produced from said mixture and containing chiefly the least volatile constltuent to rectification b means of a liquid containing another an more volatile constituent,

} withdrawing the gaseous eflluent of. this rectification, separating a portion of the most volatile constituent from said gaseous efiluent by liquefying the remaining gas. utiliz-' ing this liquid in the rectification and when the efliuent hasbeensufliciently enriched in the constituent of intermediate volatility subjecting a portion. thereof to dooling by heat interchange with a liquid to separate the least volatlle constituent therefrom.

14. A method ofrecovering argon from air, which comprises subjecting a hquid and vapors containing oxygen, nitrogen and argon to contin'uin rectification, compressing the gaseous e uent, cooling it to separate a liquid containing chiefly argon and oxygen and a gaseous residue containing practically all ofthe nitrogen, using the last-named liquid in said rectification and when the efiluent has been sufliciently enriched in argon subjecting a portion thereof to cooling to separate oxygen therefrom. 15. A method of recovering argon from air, which comprises subjecting a liquid and apors containing oxygen, nitrogen and argon to continuing rectification, compressing the gaseous efliuent, cooling it to separate a liquid containing chiefly argon and oxygen "and a gaseous residue containing ractically all of the nitrogen, using the est-named liquid in said rectification and 'whenthe eflluent has been sufliciently enriche'd in argon subjectin a portion thereof to cooling by heat exc an with liquid nitrogen to separate oxygen t erefrom.

16. A method of separating the constituents of gaseous mixtures, which comprises subjecting the compressed and-cooled mixture to selective liquefaction to separate a liquid enriched in the less volatile constituents and a residual gas, liquefying the residual gas, rectifying the liquid enriched in the less volatile constituents with a portion of the liquefied residual gas, subjecting the liquid product of therrectification to an auxiliary rectification, cooling the gaseous product of the auxiliary rectification by heat interchange with the balance of the liquefied residual gas to separate the 'least volatile constituent therefrom, recompressing the remainder of the gaseous product of the auxiliary rectification, subjecting it to a partial liquefaction to separate the most volatile constituent therefrom and utilizing the liquid thus obtained in the auxiliary rectification.

17. A method of recovering argon from 8.11, which comprises subjecting a hquid and vapors contain ng oxygen, nitrogen and argon to continuing rectification, coolin the gaseous efliuent by heat interchange with a liqpid, vcompressing the' aseous eflluent, su jecting the compressed efiluent to a liquefaction operation toseparate a liquid containing chiefly argon and oxygen and a gaseous residue containing practically all of the nitrogen, and using the last named liquid in said rectification.

18. A method of separating the constituents of ternary gaseous mixturgs, which com rises subjecting a liquid and its vapors pro need from said mixture and containing chiefly the least volatile constituent to rectification by means of a liquid containing another and more volatile constituent, subjecting the gaseous eflluent of this. rectification to heat-interchange with a liquid, thereby separating additional quantities of the least volatile constituent, compressing the remainder of the eflluent, subjecting it to a liquefaction operation to separate a liquid containing the two less volatile constituents and a residual gas consisting of the most volatile constituent and utilizing this liquid for usein said rectification, and separate means for subi'ecting the remainder of the v 'efiiuent'to coo ing to liquefy anoth'er con- 6 stituent.

.20. In an apparatus for separatingthe constituentsof gaseous mixtures, the coma :binati'on of. means for rectifying aL liquid 7 and wepors r containing said const tuents,

9' means \-for recompressing and cooling at portionfifthe gaseous .efliuent from the recti foruse, in said-rectification, and a bajskward-retui n condenser above the rectlfy- 'as a gaseous residue and to produce a liquid 'by anot er constituent is liquefied.

, v ,fieation toseparate one of the constituents as a gaseous residue and toproduce a liquid ing means to cool the remainder of the ef-g fluent b hest-exchange with at liquid where- 21. 'In an apparatus for separating the constituents of gaseous mixtures, the,com-- bination of means for rectifying a liquid and vapors containing said constituents,

means for subjecting the eifluent from-the rectification t'o heat-interchange 'witha} liquid, and separate means for recompressing and cooling" the efliuent to separate one of the constituents as'a gaseous residue and to produce a liquid for use in said rectification'l 7 In testimony whereof aiiix signa- 30 mm. 4 r g CLAUDE c. VAN NUYS. 

